Acoustic transducer with high sensitivity

ABSTRACT

An acoustic transducer with high sensitivity includes a base plate, a back plate and a vibrating membrane. The vibrating membrane is peripherally fixed to the base plate and covers an opening of the base plate. The back plate has a positioning member connected between the back plate and the vibrating membrane, so as to define at least one vibratile portion that is arranged annularly by a plurality of elastic members. Thereby, the vibratile portion has a reduced deformable width and increased rigidity, so can effectively improve its acoustically receiving sensitivity and signal-to-noise ratio.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to acoustic transducers, and more particularly to an acoustic transducer whose vibrating membrane is centrally provided with a positioning member so as to define a vibratile portion that can vibrate freely, wherein the vibratile portion is peripherally provided with a plurality of elastic members that allow the vibratile portion to perform piston-like vertical vibration, thereby enhancing the sensitivity of the acoustic transducer.

2. Description of Related Art

MEMS microphones are known to have advantages of being compact and easy to manufacture, so are extensively used in mobile phones. A conventional acoustic transducer 80, as shown in FIG. 1, has a base plate 81, a back plate 82 and a vibrating membrane 83. The vibrating membrane 83 covers an opening 811 of the base plate 81, and the back plate 82 is deposited on the base plate 81 and separated from the vibrating membrane 83 by a gap 84. An electrode unit 85 is arranged on the back plate 82 and there is a fixing portion 821 that fixes an outer periphery of the vibrating membrane 83. Thereby, when the acoustic transducer 80 receives an acoustic wave, the vibrating membrane 83 vibrates and changes its distance from the electrode unit 85, causing change of capacitance.

When the acoustic transducer 80 receives acoustic waves and the vibrating membrane 83 deforms in the direction along which the acoustic waves advance, since the vibrating membrane 83 only has its periphery fixed to the base plate 81, the vibrating membrane 83 has its central part deforming more than its peripheral part, so the vibrating membrane 83 now forms an arc with its opening facing downward. This uneven deformation can cause the effective sensing area A of the vibrating membrane 83 significantly smaller than the entire area of the vibrating membrane 83, leading to negative impact on the acoustic transducer 80 in terms of sensitivity and signal-to-noise ratio. Existing approaches to preventing the vibrating membrane from the arched deformation include increasing the thickness of the vibrating membrane and reducing the total area of the vibrating membrane in order to increase the vibrating membrane's rigidity. However, these existing approaches can be subject to increase manufacturing process complexity and manufacturing cost. Hence, there is a need for a feasible technical scheme for solving this problem.

BRIEF SUMMARY OF THE INVENTION

In view of this, the primary objective of the present invention is to provide an acoustic transducer with high sensitivity, wherein the acoustic transducer can have the deformable width of its vibrating membrane controlled so that the vibrating membrane can perform a nearly parallel movement, thereby effectively improving its acoustically receiving sensitivity and signal-to-noise ratio.

For achieving the above objective, the present invention provides an acoustic transducer with high sensitivity, which comprises a base plate, a back plate and a vibrating membrane. The vibrating membrane has its periphery fixed to the base plate and covers an opening of the base plate. The back plate has a positioning member that is connected to the vibrating membrane, so as to define at least one vibratile portion. There are a plurality of elastic member arranged annularly along the periphery of the vibratile portion.

Thereby, the present invention can make the deformable width of the vibratile portion smaller than its entire width without changing the vibrating membrane's thickness or dimensions. The reduced deformable width can increase the rigidity of the vibratile portion. When the acoustic transducer receives acoustic waves, the elastic members deform first and make the vibratile portion to perform vertical vibration in the form of a nearly parallel movement, so as to effectively improve the acoustically receiving sensitivity and signal-to-noise ratio. The present invention is also helpful to the control of process stability and manufacturing costs.

Preferably, the positioning member is a solid column or a hollow column or is formed by a plurality of solid posts to define a single vibratile portion or two or more vibratile portions.

Preferably, the vibrating membrane is round and the positioning member is connected to a center of the vibrating membrane, so that the vibratile portion is circular. Alternatively, when the vibrating membrane is rectangular, the positioning member is linearly presented to define two rectangular vibratile portions that both perform even deformation and movement.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a conventional acoustic transducer.

FIG. 2 is a transverse cross-sectional view of an acoustic transducer according to one embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view of the acoustic transducer of FIG. 2 taken along Line 3-3.

FIG. 4 is a cross-sectional view of an acoustic transducer according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view of an acoustic transducer according to a third embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

For further illustrating the features of the present invention, the following description, in conjunction with the accompanying drawings and preferred embodiments, is set forth as below. Referring to FIG. 2 and FIG. 3, according to a first embodiment of the present invention, an acoustic transducer 1 mainly comprises a base plate 10, a vibrating membrane 20, a back plate 30 and a plurality of elastic members 40. The structure and configuration of the components are described in the following sections.

As shown in FIG. 2, the base plate 10 is formed by a silicon bottom layer 11 and an insulation layer 12 deposited on the silicon bottom layer 11. The base plate 10 has a hollowed portion 13 extending between two sides of the base plate 10 and forming a round opening 14 at the insulation layer 12 for acoustic waves to pass therethrough.

The vibrating membrane 20 is peripherally fixed to the base plate 10 and covers the opening 14. In the present embodiment, the vibrating membrane 20 is round. Of course, people skilled in the art may make the vibrating membrane be square or in other geometric shapes and correspondingly modify the appearance of the opening 14.

The back plate 30 is covered on the insulation layer 12 and has a surface 35 facing the base plate 10. The surface 35 is separated from the vibrating membrane 20 by a gap G. In addition, the back plate 30 has a positioning member 31 extending from the surface 35 toward the vibrating membrane 20, for prohibiting the central part of the vibrating membrane 20 from vibrating. The back plate 30 further has a plurality of sound holes 33 for allowing acoustic waves to pass therethrough. The number of the sound holes 33 may vary according to practical needs. Depending on the means of packaging, the acoustic transducer 1 may have acoustic waves transmitted from the sound holes 33 to the vibrating membrane 20. Referring to FIG. 3, the positioning member 31 serves to define a vibratile portion 21 that can vibrate freely. In the present embodiment, the vibratile portion 21 is a circular shape, and it exists between the periphery of the positioning member 31 and the periphery of the vibrating membrane 20 that is connected to the base plate 10. In the present embodiment, the positioning member 31 is a solid column. People skilled in the art may make the positioning member 31 be a solid or hollow column of other geometric shapes, so as to change the geometric shape and number of the vibratile portion 21.

The elastic members 40 are arranged annularly along the inner and outer peripheries of the vibratile portion 21 that are relatively adjacent to and far from the positioning member 31, respectively. The number of the elastic members 40 may vary according to practical needs.

When an acoustic wave passes through the hollowed portion 13 or the sound holes 33 and reaches the vibrating membrane 20, as shown in FIG. 2 and FIG. 3, the elastic members 40 that are innately more elastic than the vibrating membrane 20 deform first. Plus, the deformable width R of the vibratile portion 21 is smaller than the entire width of the vibrating membrane 20, so the rigidity is increased, and the deformation is reduced. As a result, in response to the acoustic wave, the vibratile portion 21 and the elastic member 40 can perform a nearly parallel movement. As compared to a case without the positioning member 31, though some sensing area of the vibrating membrane 20 is sacrificed, the valid sensing area is actually increased. This allows the acoustic transducer 1 to have improved acoustically receiving sensitivity and signal-to-noise ratio under the condition that the thickness and material of the vibrating membrane 20 are not changed.

Referring to FIG. 4, in a second embodiment of the present invention, an acoustic transducer is structurally similar to the first embodiment except that the positioning member 31 is a hollow column whose outer diameter is smaller than the diameter of the opening 14. At this time, the positioning member 31 divides the vibrating membrane 20 into two regions, namely two vibratile portions 21 positioned inside and outside the positioning member 31, respectively. Each of the vibratile portions 21 has its peripheries provided with plural elastic members 40, so that the vibratile portions 21 can correspond to different sound dynamic ranges.

In a third embodiment of the present invention, as shown in FIG. 5, an acoustic transducer is structurally similar to the first embodiment except that the opening 14 is square and the vibrating membrane 20 is rectangular. The positioning member 31 comprises a plurality of connecting posts arranged in a direction parallel to the width side W of the vibrating membrane 20. In this case, the positioning member 31 also limits the vibration of the vibrating membrane 20 to some certain regions it defines. Herein, two vibratile portions 21 are defined and peripherally provided with plural elastic members 40, such that the deformable width of the vibratile portions 21 can be also adjusted to enhance the effective sensing area A.

The present invention has been described with reference to the preferred embodiments and it is understood that the embodiments are not intended to limit the scope of the present invention. Moreover, as the contents disclosed herein should be readily understood and can be implemented by a person skilled in the art, all equivalent changes or modifications which do not depart from the concept of the present invention should be encompassed by the appended claims. 

What is claimed is:
 1. An acoustic transducer with high sensitivity, comprising: a base plate having an opening; a back plate; a vibrating membrane being peripherally fixed to the base plate and covering the opening; a positioning member connecting between the back plate and the vibrating membrane, so as to define at least one vibratile portion; and a plurality of elastic members arranging annularly along a periphery of the vibratile portion.
 2. The acoustic transducer of claim 1, wherein the positioning member is a solid column.
 3. The acoustic transducer of claim 1, wherein the positioning member is a hollow column.
 4. The acoustic transducer of claim 1, wherein the positioning member is formed by a plurality of connecting posts.
 5. The acoustic transducer of claim 1 , wherein the positioning member extends from the back plate toward the vibrating membrane so as to get connected with the vibrating membrane.
 6. The acoustic transducer of claim 1, wherein the positioning member extends from the vibrating membrane toward the back plate so as to get connected with the back plate.
 7. The acoustic transducer of claim 1, wherein the vibrating membrane is round, and the positioning member is connected to a center of the vibrating membrane, so as to make the vibratile portion be circular.
 8. The acoustic transducer of claims 3, wherein the vibrating membrane is round, and the positioning member is connected to a center of the vibrating membrane, so as to make the at least one vibratile portion be in an amount of two.
 9. The acoustic transducer of claims 4, wherein the vibrating membrane is round, and the positioning member is connected to a center of the vibrating membrane, so as to make the at least one vibratile portion be in an amount of two.
 10. The acoustic transducer of claims 1, wherein the vibrating membrane is rectangular, and the positioning member is linearly arranged, so as to make the at least one vibratile portion be in an amount of two and all of them be rectangular. 